Variable direction of view endoscopes allow a user to change the endoscopic viewing direction without having to change the position of the endoscope itself. Such endoscopes are useful when the user wants to see structures which are beside or behind the tip of the endoscope but can not easily move the endoscope shaft because of anatomical constraints or constraints imposed by other surgical instruments in the operative field.
Variable direction of view endoscopy is desirable because it affords surgeons greater flexibility in their procedural approach. Increased viewing mobility improves the quality of diagnoses, as in cystoscopy for example, where a typical diagnostic screening involves inspecting the interior surface of the bladder for lesions or tumors. The ability to look laterally and retrograde is important when doing this type of diagnosis because it makes it possible to visually cover the entire bladder surface, including the entrance region near the bladder neck. In ear-nose-throat and neurosurgical procedures, variable viewing is desired because the procedures are delicate, and the entrance ports are small. It is therefore not possible to manipulate the endoscope significantly without injuring the patient. The ability to look sideways and backwards is important however during and after tumor resection when it is necessary to keep track of tumor fragments, which if not caught can nucleate new tumors. Laparoscopy, another surgical discipline, imposes fewer maneuvering constraints but still benefits markedly from variable direction viewing because it allows surgeons to get better observation angles during a procedure and increases diagnostic capabilities. Also, because of the greater viewing versatility, variable direction of view endoscopes can minimize conflicts with other tools and can simplify surgical planning by their ability to achieve standard viewing angles from nonstandard positions, allowing the surgeon to keep the endoscope “off to the side” but still get the desired view.
With commercially available variable direction of view endoscopes, the user typically changes the line of sight by using knobs or levers which mechanically actuate optomechanics at the tip of the scope. For example, commonly owned U.S. Pat. No. 7,427,263 includes examples of variable direction of view endoscopes actuated by knobs and levers. Rotating a knob or moving a lever back and forth between two limits moves the endoscopic line of sight back and forth within a viewing range. The problems with knobs and levers are that they are complex, costly and insufficiently robust. As also shown in U.S. Pat. No. 7,427,263, electromechanical and electronic variable direction of view endoscopes may also be controlled with joysticks or buttons. A minimum of two buttons are typically used to achieve back and forth (and/or side to side) motion of the line of sight. There are often additional buttons for features such as quick return to a specified angle or to control other features, such as image capture, image-leveling, and illumination intensity.
The problem with multiple buttons is that users frequently press the wrong button because they are looking at a screen displaying the endoscopic image rather than at the buttons on the endoscope. Surgeons therefore express frustration with variable direction of view prototypes which have too many buttons. This frustration is the same as the long standing frustration surgeons have had with endoscopic camera heads which often have multiple buttons. Inevitably an incorrect button press occurs (or an incorrect joystick move) which invokes a function or move which then has to be undone.
Thus, there exists a need in the art for an improved means to control variable direction of view endoscopes.